Newest Problem
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Joined: Nov 2007
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From: Denver Metro Area, CO
I would test:
1) What is reaching the battery - red probe on the battery + post, other one to ground.
2) If you want, you can place the red probe on the output of the alternator itself, place the red probe on the alternator output.
1) What is reaching the battery - red probe on the battery + post, other one to ground.
2) If you want, you can place the red probe on the output of the alternator itself, place the red probe on the alternator output.
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Elder User
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Battery is charged to 14.5v. With truck running the alternator is putting off 12.95v by putting + probe on + battery post and - probe on braided ground strap. With truck off the wire that gets melting hot when touching - probe to - battery post and + probe to hot wire there are 11.5v. That is with he truck off. Is that supposed to be like that? I then redid the alternator test as above with truck off and there was no voltage that I detected.
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Joined: Nov 2007
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From: Denver Metro Area, CO
What you're describing is confusing, why do you use two different ground points for measurement? The only braided ground I'm familiar with in the general area is between the hood & firewall.
Less confusing: Put the probes directly on the battery posts, not on any cables. With the probes in the exact same places, what are the voltage readings with the engine running and with it not running?
I'm sorry, I should have never sent you to read the diagnostics in the EVTM; I did that, they send you to the shop manual for the true diagnostics (which I don't have for your configuration with a 2G alternator).
Less confusing: Put the probes directly on the battery posts, not on any cables. With the probes in the exact same places, what are the voltage readings with the engine running and with it not running?
I'm sorry, I should have never sent you to read the diagnostics in the EVTM; I did that, they send you to the shop manual for the true diagnostics (which I don't have for your configuration with a 2G alternator).
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Elder User
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Battery truck off: 11.84v
Truck on: 11.90v
Battery neg post to alternator pos wire that gets hot: 11.64v
My alternator mount bracket has a braided ground strap that hooks to the frame. I also have one that hooks from the hood to the firewall and one other that connects the the firewall and is not connected on the other side near the heater ( looks like wire crimp on disconnected end, but it has been like that for a very long time by the looks of it.)
Truck on: 11.90v
Battery neg post to alternator pos wire that gets hot: 11.64v
My alternator mount bracket has a braided ground strap that hooks to the frame. I also have one that hooks from the hood to the firewall and one other that connects the the firewall and is not connected on the other side near the heater ( looks like wire crimp on disconnected end, but it has been like that for a very long time by the looks of it.)
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Joined: Nov 2007
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From: Denver Metro Area, CO
By "truck on" I'm guessing this means with the engine running and not just with the ignition turned on, correct?
You should have a ground from the rear of the engine to the firewall, my guess is that's not connected right now but likely isn't the cause of your problem.
You also said something about there being a spark when you reconnected the alternator output to the starter solenoid, correct?
You should have a ground from the rear of the engine to the firewall, my guess is that's not connected right now but likely isn't the cause of your problem.
You also said something about there being a spark when you reconnected the alternator output to the starter solenoid, correct?
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From: Denver Metro Area, CO
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Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
But I just thought of something... a 1970s sedan engine likely has a 1G alternator, and a mid-80s truck charging system used a 2G... we have no idea what you're configuration is, can you post some pictures everything? Particularly the front & rear of the alternator and what would be the voltage regulator on a 1G system near the starter solenoid.
I would also be inclined to remove the alternator and take it to a parts store to have it tested.
I would also be inclined to remove the alternator and take it to a parts store to have it tested.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
If post #35 means that he disconnected the charge cable from the starter relay (solenoid) with the engine running it's no wonder the alternator got smoking (boiling) hot.
It is trying to balance system voltage but has no connection to the battery.
It is trying to balance system voltage but has no connection to the battery.
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Elder User
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Side view
Bottom view
Back of alternator. Stuck camera behind and took picture, but it did not turn out to well. If I need to I can figure out a way to get a better pic.
Front view
Bracket with beaded ground going to body
Where it hooks to solenoid. You can see wher it melted through the thick rubber around the connector.
Front view of solenoid. It is behind the red pos wire.
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Elder User
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Did not take it that way at all. Have fun at the drag strip. You racing?
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Elder User
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I reread post 35 and it was confusing. I have fixed it. I unhooked the wire from the solenoid when the truck was off.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Pretty good pictures.
So if I get it right it is the big red cable (from batt + ?) on the solenoid that gets hot?
When does this get hot when running or just after you start the truck and then it cools down?
What does the black wire(s) behind the red cable go to? Is that the power feed to the inside of truck?
Where does the ALT out put wire tie into the big red cable or the batt?
I/we would like to see where the batt - cable goes to, is it motor or frame?
I would also clean the braided wire end that bolts to the body so we know it has a good connection.
Dave ----
So if I get it right it is the big red cable (from batt + ?) on the solenoid that gets hot?
When does this get hot when running or just after you start the truck and then it cools down?
What does the black wire(s) behind the red cable go to? Is that the power feed to the inside of truck?
Where does the ALT out put wire tie into the big red cable or the batt?
I/we would like to see where the batt - cable goes to, is it motor or frame?
I would also clean the braided wire end that bolts to the body so we know it has a good connection.
Dave ----